Ammonia Preparation

The Haber process synthesises ammonia from nitrogen and hydrogen by the reaction N_2 + 3H_2 ⇌ 2NH_3, which is exothermic and proceeds with a decrease in the number of gas molecules. By Le Chatelier's principle, high pressure favours the side with fewer gas molecules, so high pressure increases the yield of ammonia. Although low temperature thermodynamically favours the exothermic forward reaction, very low temperatures make the rate impractically slow, so an optimum moderate temperature around 700 K is used as a compromise between yield and rate. An iron catalyst with promoters speeds the attainment of equilibrium without altering its position. The option of high temperature and low pressure would lower the yield on both counts. The option of low pressure and no catalyst gives a poor, slow yield. The option of very high temperature alone shifts equilibrium backward. These optimised conditions are a standard NCERT industrial example. Such questions reward conceptual clarity, since a student who truly grasps Haber process can solve many superficially different variants with the same approach. Plausibility check: choosing high pressure and a moderate catalysed temperature balances Le Chatelier's principle against reaction kinetics, confirming the chosen conditions.